Have any of you parents moved far away from your kids?

My ex, who is bipolar, left me and the kids about 3 years ago for online affairs. She is on online affair # 15 right about now. She hasnt really showed much interest in them outside of her every other weekend visits. She claims to miss and love them but never ever comes to get them outside of every other weekend. We live in the USA but she is now moving to Canada to live with someone she met online and where she will basically rarely ever see them. How many of you parents have done this? How did you as the responsible parent handle seeing your kids in so much pain because of her actions? I for one think its for the best to see her go so the kids woint have to deal with it. Am I wrong for thinking that?
Wow! I will never understand how you can put someone else who you left your marraige for before your kids.